Hi,
I would like to propose a change in the behavior of the OS::Mistral::Workflow
resource signal.
CURRENT:
The OS::Mistral::Workflow resource type is expecting the following request body
on resource signal request:
{
"input": {
...
},
"params": {
...
}
}
The input section is optional and if exists it will be passed to the workflow
execution as inputs
The params section is also optional and if exists it will be passed to the
workflow execution as parameters.
The problem this approach creates is that external systems many times send a
predefined body that you cannot control and it is obviously not in the format
the resource is expecting.
So you basically have no way to pass the information from the request body to
the workflow execution.
SUGGESTION:
OS::Mistral::Workflow will treat the root of the JSON request body as input
parameters.
That way you will be able to use external systems by making sure your WF inputs
are aligned with what the external system sends.
For example, if you try to put the WF alarm_url as a Ceilometer alarm action -
Ceilometer will send a request similar to:
{
"severity": "low",
"alarm_name": "my-alarm",
"current": "insufficient data",
"alarm_id": "895fe8c8-3a6e-48bf-b557-eede3e7f4bbd",
"reason": "1 datapoints are unknown",
"reason_data": {
"count": 1,
"most_recent": null,
"type": "threshold",
"disposition": "unknown"
},
"previous": "ok"
}
The WF could get this info as input if it will be defined like so:
my_workflow:
type: OS::Mistral::Workflow
properties:
input:
current: !!null
alarm_id: !!null
reason: !!null
previous: !!null
severity: !!null
alarm_name: !!null
reason_data: !!null
The (least used) "params" section can be passed in an custom HTTP header and
the OS::Mistral::Workflow will read those from the header and pass it to the WF
execution.
Remember, we are trying to solve the problem where you can't influence the
request format - so in any case the signal will not get the params in the
request body.
If the WF of the user must receive params, the user will always be able to
create a wrapper WF with only inputs that starts the orig WF with inputs and
params.
In order to make this non-backward compatible change, I suggest to add a
property "params_alarm_http_header_name" to the OS::Mistral::Workflow. If null
the params are expected to be in the body as today.
If not null - the request should have a header with that name and the value
will be a string representing a JSON dict.
I would really like to hear your opinion and comments.
Thanks.
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